1. Field of the Invention
The invention relates to a light-emitting diode, and more particularly, to a light-emitting diode with high lighting efficiency.
2. Description of the Prior Art
Nowadays, applications of the light-emitting diode are everywhere in our daily life. There are different kinds of light-emitting diodes widely utilized in various products, e.g. key-switch systems, backlight modules, vehicle illuminations, decorating lamps, remote controllers, etc. To ensure that the light-emitting diode have better reliability and lower power consumption, it demands the light-emitting diode to maintain high lighting efficiency.
Please refer to FIG. 1. FIG. 1 is a diagram illustrating a light-emitting diode 1 in prior art. As shown in FIG. 1, the light-emitting diode 1 includes a substrate 10, an N-type GaN layer 11, a light-emitting layer 12, a P-type GaN layer 13, an electrode 14 and an electrode 15. In order to drive the P-type GaN layer 13 and the N-type GaN layer 11 for operating the light-emitting diode 1, the electrode 15 is formed on the P-type GaN layer 13 and the electrode 14 is formed on the N-type GaN layer 11.
Theoretically, the lighting efficiency of the light-emitting diode is related to the internal quantum yield and the light-extraction efficiency. The internal quantum yield is affected by characteristic and quality of the material. The light-extraction efficiency is the radio ratio defined by the radiation from the light-emitting diode to the surrounding air or the packed epoxy. Although there are lots of disclosed designs about different structures of the light-emitting diodes, it is still a critical problem to find a light-emitting diode structure capable of operating under high light-extraction efficiency and high lighting efficiency.